Due to its vast size and range of altitudes, Argentina possesses a wide variety of climatic regions, ranging from the hot subtropical region in the north to the cold subantarctic in the far south. The Pampas region lies between those and featured a mild and humid climate. Many regions have different, often contrasting, microclimates. In general, Argentina has four main climate types: warm, moderate, arid, and cold in which the relief features, and the latitudinal extent of the country, determine the different varieties within the main climate types.
Northern parts of the country are characterized by hot, humid summers with mild, drier winters, and highly seasonal precipitation. Mesopotamia, located in northeast Argentina, has a subtropical climate with no dry season and is characterized by high temperatures and abundant rainfall because of exposure to moist easterly winds from the Atlantic Ocean throughout the year. The Chaco region in the center-north, despite being relatively homogeneous in terms of precipitation and temperature, is the warmest region in Argentina, and one of the few natural areas in the world located between tropical and temperate latitudes that is not a desert. Precipitation decreases from east to west in the Chaco region because eastern areas are more influenced by moist air from the Atlantic Ocean than the west, resulting in the vegetation transitioning from forests and marshes to shrubs. Northwest Argentina is predominantly dry, hot, and subtropical although its rugged topography results in a diverse climate.
Central Argentina, which includes the Pampas to the east, and the Cuyo region to the west, has a temperate climate with hot summers and cool, drier winters. In the Cuyo region, the Andes obstruct the path of rain-bearing clouds from the Pacific Ocean; moreover, its latitude coincides with the subtropical high. Both factors render the region dry. With a wide range of altitudes, the Cuyo region is climatically diverse, with icy conditions persisting at altitudes higher than . The Pampas is mostly flat and receives more precipitation, averaging in the western parts to in the eastern parts. The weather in the Pampas is variable due to the contrasting air masses and frontal storms that impact the region. These can generate thunderstorms with intense hailstorms and precipitation, and are known to have the most frequent lightning, and highest convective cloud tops, in the world.
Patagonia, in the south, is mostly arid or semi–arid except in the extreme west where abundant precipitation supports dense forest coverage, glaciers, and permanent snowfields. Its climate is classified as temperate to cool temperate with the surrounding oceans moderating temperatures on the coast. Away from the coast, areas on the plateaus have large daily and annual temperature ranges. The influence of the Andes, in conjunction with general circulation patterns, generates one of the strongest precipitation gradients (rate of change in mean annual precipitation in relation to a particular location) in the world, decreasing rapidly to the east. In much of Patagonia precipitation is concentrated in winter with snowfall occurring occasionally, particularly in the mountainous west and south; precipitation is more evenly distributed in the east and south. One defining characteristic is the strong winds from the west which blow year-round, lowering the perception of temperature (wind chill), while being a factor in keeping the region arid by favouring evaporation.
Definition of the regions In general, Argentina has four main climate types: warm, moderate, arid, and cold, all determined by the expanse across latitude, range in altitude, and relief features. The vast size, and wide range of altitudes, contribute to Argentina's diverse climate. Argentina possesses a wide variety of climatic regions ranging from subtropical in the north to subantarctic in the far south. Lying between those is the Pampas region, which features a mild and humid climate. Under the Köppen climate classification, Argentina has 11 different climate types: Humid Subtropical (Cfa, Cwa), moderate oceanic (Cfb), warm semi-arid (BSh), subtropical highland oceanic (Cwb), warm desert (BWh), cold semi–arid (BSk), cold desert (BWk), moderate Mediterranean (Csb), cold oceanic (Cfc), and tundra (ET). Consequently, there is a wide variety of biomes in the country, including subtropical rain forests, semi-arid and arid regions, temperate plains in the Pampas, and cold subantarctic in the south. However, despite the diversity of biomes, about two-thirds of Argentina is arid or semi-arid. Argentina is best divided into six distinct regions reflecting the climatic conditions of the country as a whole. From north to south, these regions are Northwest, Chaco, Northeast, Cuyo/Monte, Pampas, and Patagonia. Each climatic region has distinctive types of vegetation.
Argentina claims sovereignty over part of Antarctica, which includes the Antarctic Peninsula and a triangular section extending to the South Pole, delimited by the 25° West and 74° West meridians and the 60° South parallel. However, all claims are suspended by the Antarctic Treaty System, of which Argentina is a founding signatory and permanent consulting member. Argentina also claims sovereignty over the Falkland Islands (), and South Georgia and the South Sandwich Islands (). However, the United Kingdom exercises de facto control over both the Falkland Islands, and South Georgia and the South Sandwich Islands, both as British Overseas Territories.
Mesopotamia
The region of Mesopotamia includes the provinces of Misiones, Entre Ríos and Corrientes. It lies between the Uruguay and Paraná rivers, which serve as natural borders for the region.
It has a humid subtropical climate (Cfa according to the Köppen climate classification). whose main features are high temperatures and abundant rainfall throughout the year. This year-round rainfall occurs because most of the region lies north of the subtropical high pressure belt even in winter, exposing it to moist easterly winds from the Atlantic Ocean throughout the year. Water deficiencies and extended periods of drought are uncommon, and much of the region has a positive water balance (i.e. the precipitation exceeds the potential evapotranspiration).
Precipitation Mesopotamia is the wettest region in Argentina with average annual precipitation ranges from less than in the southern parts, to approximately in the eastern parts.Precipitation is slightly higher in summer than in winter, and generally decreases from east to west and from north to south. Summer (December–February) is the most humid season, with precipitation ranging from . Fall (March–May) is the rainiest season, with many places receiving over . Most of the rainfall during summer and fall is caused by convective thunderstorms. Winter (June–August) is the driest season, with a mean precipitation of throughout the region. Most of the winter precipitation is the result of synoptic scale, low pressure weather systems (large scale storms such as extratropical cyclones), particularly the sudestada, which often bring long periods of precipitation, cloudiness, cooler temperatures, and strong winds. Snowfall is extremely rare and mainly confined to the uplands of Misiones Province where the last significant snowfall occurred in 1975 in Bernardo de Irigoyen. Spring (September–November) is similar to fall with a mean precipitation of .
Temperatures Mean annual temperatures range from in the south to in the north. Summers are hot and humid while winters are mild. The mean January temperature throughout most of the region is except in the uplands of Misiones Province where they are lower owing to its higher elevation. During heat waves, temperatures can exceed in the summer months, while in the winter months, cold air masses from the south can push temperatures below freezing, causing frost. However, such cold fronts are brief, and are less intense than in areas further south or at higher altitudes.
Statistics for selected locations
Chaco
The Chaco region in the center-north completely includes the provinces of Chaco, and Formosa. Eastern parts of Jujuy Province, Salta Province, and Tucumán Province, and northern parts of Córdoba Province and Santa Fe Province are part of the region. As well, most of Santiago del Estero Province lies within the region.
The region has a subtropical climate. Under the Köppen climate classification, western parts have a semi-arid climate (Bs) while the east has a humid subtropical climate (Cfa). Chaco is one of the few natural regions in the world located between tropical and temperate latitudes that is not a desert. Precipitation and temperature are relatively homogeneous throughout the region. The general atmospheric circulation influences the climate of the region, primarily by two permanent high pressure systems – the South Pacific High and the South Atlantic High – and a low pressure system that develops over northeast Argentina called the Chaco Low. The interaction between the South Atlantic High and the Chaco Low generates a pressure gradient that brings moist air from the east and northeast to eastern coastal and central regions of Argentina. In summer, this interaction strengthens, favouring the development of convective thunderstorms that can result in heavy rainfall. In contrast, winters are dry due to these systems weakening, and the lower insolation that weakens the Chaco Low, and the northward displacement of westerly winds. During the entire year, the South Pacific High influences the climate by bringing cold, moist air masses originating in Patagonia leading to cold temperatures and frost, particularly during winter. Summers feature more stable weather than winter since the South Atlantic and South Pacific highs are at their southernmost positions, making the entrance of cold fronts more difficult.
Precipitation Mean annual precipitation ranges from in the eastern parts of Formosa Province to a low of in the west and southwest. Most of the precipitation is concentrated in the summer and decreases from east to west. Summer rains are intense, and torrential rain is common, occasionally causing floods and soil erosion. During the winter months, precipitation is sparse. Eastern areas receive more precipitation than western areas since they are more influenced by moist air from the Atlantic Ocean. This penetrates the eastern areas more than the west, bringing it more precipitation. As a result, the vegetation differs with eastern areas being covered by forests, savannas, marshes, and subtropical wet forest, while western areas are dominated by medium and low forests of mesophytic and xerophytic trees, and a dense understory of shrubs and grasses. The western part has a pronounced dry winter season while the eastern parts have a slightly drier season. In all parts of the region, precipitation is highly variable from year to year. The eastern part of the region receives just enough precipitation to have a positive water balance. By contrast, the western parts of the region have a negative water balance (the potential evapotranspiration exceeds the precipitation) owing to lower precipitation.
Temperatures The Chaco region is the hottest in Argentina, with a mean annual temperature of . With mean summer temperatures reaching , the region has the hottest summers in the country. Winters are mild and brief, with mean temperatures in July ranging from in the northern parts to in the southernmost parts. Absolute maximum temperatures can reach up to while during cold waves, temperatures can fall to . Eastern areas are more strongly influenced by maritime climate than western areas, leading to a smaller thermal amplitude (difference between average high and average low temperatures). This results in absolute maximum and minimum temperatures being and in the east compared to more than and in the west.